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Zero outward flow velocity for plasma in a heliosheath transition layer
Stamatios M Krimigis1, Edmond C Roelof, Robert B Decker
1Applied Physics Laboratory, The Johns Hopkins University, Laurel, Maryland 20723, USA. tom.krimigis@jhuapl.edu
Nature
|June 17, 2011
Summary
Voyager 1 has entered a zero-velocity plasma layer in the heliosheath, suggesting proximity to the heliopause. This finding challenges models of the heliosheath boundary.
Area of Science:
- Space Physics
- Heliophysics
- Plasma Physics
Background:
- Voyager 1 crossed the solar wind termination shock in 2004, entering the heliosheath.
- The heliosheath is a region of energetic ions and electrons beyond the termination shock.
- Voyager 1 is currently approximately 22 AU past the termination shock crossing.
Purpose of the Study:
- To determine the bulk velocity of plasma in the heliosheath.
- To investigate Voyager 1's position relative to the heliopause.
- To compare observed plasma flow with theoretical models of the heliosheath.
Main Methods:
- Utilizing measurements of energetic ion distribution anisotropy.
- Analyzing the bulk velocity of plasma in the radial-transverse plane.
- Tracking changes in the radial component of plasma velocity over time.
Main Results:
- The radial velocity of plasma has decreased linearly from ~70 km/s to ~0 km/s over three years.
- Voyager 1 has remained in a zero-radial-velocity region for the past eight months.
- The spacecraft appears to have entered a finite transition layer of plasma flow.
Conclusions:
- Voyager 1's entry into a zero-velocity layer suggests it is near the heliopause.
- The observed flow transition layer contradicts models predicting a sharp heliopause discontinuity.
- This finding provides new insights into the structure of the heliosheath and its boundary with interstellar space.
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